Teardown, Recordings: 1 by One Wireless Door Chime R/X QH-0031 (Quhwa QH-09D)

This post will probably make me seem like a crazy nutter, but oh well. I cannot deny the fact that I can do some very strange things from time to time.

I needed a wireless doorbell to alert me to online purchase packages being sent to my address, since the couriers and postmen never knock hard enough for me to know they’re there. I always miss them. So I decided to get two kits, both of them 1 by One branded as the transmitters and receivers were easy on batteries.

I looked at the transmitters in my rtl_433 post, and they were OEMed by Quhwa. Now it’s time to look at the receiver, for an entirely different reason.

1 by One Wireless Doorbell Receiver

So this is the receiver in question. I’m sure there are several other exteriors for the same sort of receiver, but the one I have looks like this.

1 by One Wireless Doorbell Receiver Rear

The rear has the label with the model name, and a battery hatch accepting 3xAA cells.

1 by One Wireless Doorbell Receiver Internals

Inside the doorbell, it can be seen it’s pretty empty. A small 0.5w speaker forms the “noise generating” part of the unit. A red wire snakes around the battery compartment as an antenna. The PCB seems to be quite interesting as it takes both 4.5v (i.e. 3 cells series) and 3v (i.e. two cells series) connections. This might mean that the cells are unevenly loaded during usage, and this could contribute to over-discharge of some cells or imbalance. Keep rechargeable batteries away?

1 by One Wireless Doorbell Receiver PCB Top

The PCB is marked with the real model number – QH-09D. It seems to have a provision for an LED alert as well, which was not used in this model. Two ICs are on board, one marked TX102R and the other with TR1803A. The latter is likely just a single op-amp to amplify the tones generated from the main IC.

1 by One Wireless Doorbell Receiver PCB Rear

The rear of the PCB houses the melody change switch, a few electrolytic capacitors and an adjustable inductor which is probably used to trim the receive frequency so that its most sensitive to 433.92Mhz +/- 0.5Mhz.

Why the interest in this wireless door chime?

It’s advertised as a 36 melody unit, and it has one push button to increment the melody. I wanted to see if it really has 36 melodies, and what they all were. Doing this over and over is sure to annoy the neighbours because it’s loud and repetitive, so I wanted to have some way to store it.

But then I realized that the sound of the doorbell unit itself has a particular character itself, which I would say is FM Synthesis. This harmonically rich sound is often slated as being annoying and electronic, but it has its own appeal.

Of course, some people are going to decry that the melodies will all sound like crap, but I beg to differ. There’s a retro-ness to the FM-based synthesis the door chime uses to play its music.

I used a pair of test clips and hooked the speaker output to my sound card (speaker still attached, as the loading might affect the way the chip oscillates and sounds, although unlikely). Recordings were made of each of the melodies as a 48khz 16-bit mono WAV file. I tried my best to make sure to get as true to the output as possible.

Waveforms

Interestingly, the output was relatively unfiltered and very rich in harmonics. It was such a problem that crosstalk between traces led to the jack-sense utility becoming super-confused, thinking that things have been plugged in or removed due to voltage potential changes at adjacent jacks. But this rich harmonic signature is a “quality” of the squarey nature of the FM synthesis involved.

Harmonics

It appears from a quick examination that the unit uses only three voices, each with its own envelope control, with three different waveforms (square, sine and impulse) it seems. I could be wrong, but it explains the limited number of notes. Some of the compositions are “impressive” when these hardware limitations are taken into account.

So I suppose this serves as a melody directory for the 36-melody doorbell controllers. Other than that, I suppose you could use these samples as ringtones, to mix into other things (video productions) or just to annoy someone.

About lui_gough

I'm a bit of a nut for electronics, computing, photography, radio, satellite and other technical hobbies. Click for more about me!
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3 Responses to Teardown, Recordings: 1 by One Wireless Door Chime R/X QH-0031 (Quhwa QH-09D)

  1. Tom says:

    Interesting, I googled it to see who made them as doing some tests my self.

  2. Zackary E. Jenkins says:

    I’m really happy that you posted this I have a much older model, and I’m troubleshooting a failure to link. Can’t tell if it is the receiver or transmitter that is malfunctioning. I’m just messing with it at work, so when I get home olI’ have to take out the meter and see what’s up.

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